Biological Molecules Flashcards
What are 3 types of proteins?
- enzymes e.g. amylase
- transport proteins e.g. channels
- signal proteins e.g. insulin
- defensive proteins e.g. antibodies
What are the 5 components that make up amino acids?
Nitrogen, carbon, hydrogen, oxygen and sometimes sulphur
What is the general structure of an amino acid?
A central carbon is joined to an amine group (a nitrogen bonded to two hydrogens), a carboxyl group (a carbon bonded to an hydroxyl and double bonded to an oxygen), a hydrogen and the ‘R’ group
How do peptide bonds form between amino acids?
Two amino acids join together to form a dipeptide via a condensation reaction.
The hydroxyl (OH) from one amino acid reacts with a hydrogen (H) from the amine group in the other amino acid to form water and a peptide bond.
What are the four levels of protein organisation?
Primary, secondary, tertiary and quaternary
What is the primary structure?
The number and sequence of amino acids in the polypeptide.
Why is the primary structure important?
It will determine the ultimate shape and function of a protein. Any change can alter its shape and prevent it from carrying out its function.
What is the secondary structure?
The initial folding/coiling of a polypeptide into alpha helixes and beta pleated sheets. These are maintained by hydrogen bonds.
What is the tertiary structure?
It is the further folding of a polypeptide into a 3D structure. It is held together by ionic bonds between R groups and may also have disulphide bonds.
What is the quaternary structure?
When two or more polypeptide chains join together and non-protein groups may associate e.g. iron
How do you preform a biuret test?
- Add solution to test tube
- Add equal amount of biuret reagent
- If colour changes from blue to purple then peptide bonds/ proteins are present.
How do you use chromatography to identify amino acids?
- Draw a pencil line on the bottom of the chromatography paper as a start line
- Use a pipette to drop several drops on the same spot
- Place bottom of paper in solution making sure it doesn’t touch the pencil line
- Wait for paper to dry and spray with ninhydrin solution to make amino acids clearer
What is the equation of Rf value?
Rf = distance travelled by compound / distance travelled by solvent
What is an enzyme?
They are biological catalysts that speed up the rate of reaction by lowering the activation energy by bending bonds.
What is the activation energy?
The minimum energy required for a successful chemical reaction.
What is the structure of an enzyme?
They have specific 3D tertiary structures with an active site which only a complimentary substrate can bind to.
What is the induced fit theory?
Before a reaction, the active site is not complimentary. The active sites shape changes, as the substrate binds, to form an enzyme-substrate complex. This distorts the bonds in the substrate leading to a reaction.
What are the four factors that affect enzyme action?
- Temperature
- pH
- Inhibitors
- Substrate or enzyme concentration
What effect does temperature have on enzyme action?
As temperature increases, the molecules gain more kinetic energy and collide more often, forming enzyme-substrate until the optimum is reached. Beyond this, the bonds between the R groups vibrate and break, causing the substrate to no longer fit and the enzyme denatures.
What effect does pH have on enzyme action?
If the pH changes from the optimum, the charge on the R groups in amino acids are altered and the ionic bonds are broken. This alters the shape of the active site so the substrate no longer fits.
What effect do competitive inhibitors have on enzyme action?
They are a similar shape to the substrate so can bind the the active site, preventing the formation of ES complexes. This can be overcome by adding more substrate. Slow but maximum product is reached.
What effect does concentration have on enzyme action?
As the concentration of one factor (enzyme or substrate) increases, so does the rate of reaction. However, as saturation is achieved, the concentration no longer increases the rate and it plateaus. This means the other factor is the inhibiting factor.
What effect do non-competitive inhibitors have on enzyme action?
They bind to an allosteric site on the enzyme, changing the chape of the active site. This means ES complexes cannot form.
This cannot be overcome.
What is the equation of rate?
Rate = measurement/time taken
